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Time-resolved decay curves of Nb-doped (Nb, black solid curve), oxygen deficient (O, blue dot-dashed curve), and intrinsic (, red dashed curve) samples. The curves are normalized to their maximum and plotted in a semilogarithmic vertical scale. Oscillations and other minor features are due to the instrumental response function. The pulse energy is in all cases. Inset: photoluminescence spectra of the same samples. The spectra are normalized to their maximum and vertically shifted for clarity. The narrow peak seen at is due to the residual UV scattering.
An example of the global-fit curve in the case of a Nb sample. BD (blue dotted) and UD (blue dashed) decay components are plotted separately. Gray (red) circles are the data points. The black solid curve is the total fitting curve. Inset: the whole set of decays measured for different pump energies (red circles) and on which the global fit was performed (black solid lines) is shown. The pulse energy corresponding to each curve is indicated on the left of each curve.
Time-integrated decay luminescence intensity as a function of the pulse energy for Nb (black), O (dark-gray, blue online), and (light gray, red online) samples. Circles are the UD decay integrals, triangles are the BD decay integrals. The slope of each line is the BD-UD yield. Note that all samples show approximately comparable yields for the UD and BD channels.
The estimated bandwidth (reciprocal of the full width at half maximum) is found to be a linear function of the pulse energy and of the estimated pair density (upper scale). Gray (red online) circles are the data points, the (blue) solid line is the linear fit. The slope is about . The intercept is not consistent with zero because at very low energies the decay is dominated by the UD lifetime, which is energy independent.
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